1. Field:
The subject invention is in the field of shock absorbing and/or relieving apparatus, excluding apparatus which involves mechanisms such as metal springs and hydraulic energy absorbers. More specifically it is in the field of one piece pads made of resilient material and made to fit on the ends of rifle butts to cushion the blow on the user's shoulder caused by the firing of a bullet and the resultant recoil of the rifle.
2. Prior Art:
The patents listed here are a sampling of the prior art in this field and include for reference purposes some examples of mechanical devices built into the stocks of rifles:
______________________________________ 0,488,855 2,455,438 3,335,515 0,837,601 3,007,272 3,363,352 1,642,835 3,019,543 3,514,889 1,822,875 3,039,222 3,696,544 1,868,953 3,135,064 3,707,797 2,091,010 3,263,359 2,330,430 3,274,725 3,438,142 3,290,815 ______________________________________
The recoil of a rifle caused by the shooting of a bullet is known to comprise two peak loads, the first involving the acceleration of the mass of the bullet in the rifle barrel and the second being the rocket propulsion effect of the gases exiting the barrel once the bullet has left the barrel. These loads force the end of the rifle butt against the shoulder of the user of the rifle. The effects of the forcing of the butt end against the shoulder can vary widely and depend on many factors, including the distribution of the load over the area of the butt end and the functional characteristics of any apparatus attached to the butt end of minimize the magnitude of the forces applied to the shoulder. In any specific recoil there is a specific amount of work done by the recoil forces and the work can be plotted in terms of force moving the rifle a distance during the time the forces exist. Under ideal conditions, the force applied to the shoulder will be minimum if the force is constant throughout the distance the rifle recoils during the time the forces exist. Also, the effects of the force on the shoulder will be least harmful if the full butt area is in contact with the shoulder, keeping the force per unit area (pressure) on the shoulder at a minumum.
Further, the level of the recoil force is less for greater recoil deflections. However, practical considerations result in there being an optimum recoil distance in the range of 1/8" to 3/8" with 1/4" preferred.
In the prior art pads the deflection of the pad for load distribution and the deflection for leveling of the force over the deflection distance are intermingled. There is little or no opportunity for distribution deflection to occur before the bullet acceleration force reaches its peak. Also, the load distribution deflection uses deflection which would otherwise be available for force leveling. Further, if the contours of the butt end shoulder do not match well the force is apt to be concentrated on an unnecessarily small area of the shoulder, increasing the contact area and related potential for harm.
Accordingly, the objectives of the subject invention are to provide a recoil pad in which (1) deflection of the pad to achieve uniform load distribution over the area of the pad and deflection for force leveling minimizing peak loads are essentially independent; (2) the load distribution occurs while recoil force absorption is at a relatively low level and (3) the force level during the time of recoil is close to uniform and thus minimum for the amount of work and recoil deflection limit involved.